shells: move shells into own group

1 files changed, 0 insertions, 259 deletions

diff --git a/src/tools/bash.md b/src/tools/bash.md
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--- a/src/tools/bash.md
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-# bash(1)
-
-## Expansion
-
-### Generator
-
-```bash
-# generate sequence from n to m
-{n..m}
-# generate sequence from n to m step by s
-{n..m..s}
-
-# expand cartesian product
-{a,b}{c,d}
-```
-
-### Parameter
-```bash
-# default value
-bar=${foo:-some_val}  # if $foo set, then bar=$foo else bar=some_val
-
-# alternate value
-bar=${foo:+bla $foo}  # if $foo set, then bar="bla $foo" else bar=""
-
-# check param set
-bar=${foo:?msg}  # if $foo set, then bar=$foo else exit and print msg
-
-# indirect
-FOO=foo
-BAR=FOO
-bar=${!BAR}  # deref value of BAR -> bar=$FOO
-
-# prefix
-${foo#prefix}  # remove prefix when expanding $foo
-# suffix
-${foo%suffix}  # remove suffix when expanding $foo
-
-# substitute
-${foo/pattern/string}  # replace pattern with string when expanding foo
-# pattern starts with
-# '/'   replace all occurences of pattern
-# '#'   pattern match at beginning
-# '%'   pattern match at end
-
-# set programmatically with priintf builtin
-printf -v "VAR1" "abc"
-NAME=VAR2
-printf -v "$NAME" "%s" "def"
-```
-
-> Note: `prefix`/`suffix`/`pattern` are expanded as [pathnames](#pathname).
-
-### Pathname
-
-```bash
-*           match any string
-?           match any single char
-\\          match backslash
-[abc]       match any char of 'a' 'b' 'c'
-[a-z]       match any char between 'a' - 'z'
-[^ab]       negate, match all not 'a' 'b'
-[:class:]   match any char in class, available:
-              alnum,alpha,ascii,blank,cntrl,digit,graph,lower,
-              print,punct,space,upper,word,xdigit
-```
-
-With `extglob` shell option enabled it is possible to have more powerful
-patterns. In the following `pattern-list` is one ore more patterns separated
-by `|` char.
-
-```bash
-?(pattern-list)   matches zero or one occurrence of the given patterns
-*(pattern-list)   matches zero or more occurrences of the given patterns
-+(pattern-list)   matches one or more occurrences of the given patterns
-@(pattern-list)   matches one of the given patterns
-!(pattern-list)   matches anything except one of the given patterns
-```
-> Note: `shopt -s extglob`/`shopt -u extglob` to enable/disable `extglob`
-> option.
-
-## I/O redirection
-
-> Note: The trick with bash I/O redirection is to interpret from left-to-right.
-
-```bash
-# stdout & stderr to file
-command >file 2>&1
-# equivalent
-command &>file
-
-# stderr to stdout & stdout to file
-command 2>&1 >file
-```
-> The article [Bash One-Liners Explained, Part III: All about
-> redirections](https://catonmat.net/bash-one-liners-explained-part-three)
-> contains some nice visualization to explain bash redirections.
-
-### Explanation
-
-```bash
-j>&i
-```
-Duplicate `fd i` to `fd j`, making `j` a copy of `i`. See [dup2(2)][dup2].
-
-Example:
-```bash
-command 2>&1 >file
-```
-1. duplicate `fd 1` to `fd 2`, effectively redirecting `stderr` to `stdout`
-2. redirect `stdout` to `file`
-
-## Process substitution ([ref][psub])
-
-Process substitution allows to redirect the stdout of multiple processes at
-once.
-```bash
-vim -d <(grep foo bar) <(grep foo moose)
-```
-
-## Command grouping
-
-Execute commands in a group with or without subshell. Can be used to easily
-redirect stdout/stderr of all commands in the group into one file.
-```bash
-# Group commands without subshell.
-v=abc ; { v=foo; echo $v; } ; echo $v
-# foo
-# foo
-
-# Group commands with subshell.
-v=abc ; ( v=foo; echo $v; ) ; echo $v
-# foo
-# abc
-```
-
-## Argument parsing with `getopts`
-
-The `getopts` builtin uses following global variables:
-- `OPTARG`, value of last option argument
-- `OPTIND`, index of the next argument to process (user must reset)
-- `OPTERR`, display errors if set to `1`
-
-```bash
-getopts <optstring> <param> [<args>]
-```
-- `<optstring>` specifies the names of supported options, eg `f:c`
-  - `f:` means `-f` option with an argument
-  - `c` means `-c` option without an argument
-- `<param>` specifies a variable name which `getopts` fills with the last parsed option argument
-- `<args>` optionally specify argument string to parse, by default `getopts` parses `$@`
-
-### Example
-```bash
-#!/bin/bash
-function parse_args() {
-    while getopts "f:c" PARAM; do
-        case $PARAM in
-            f) echo "GOT -f $OPTARG";;
-            c) echo "GOT -c";;
-            *) echo "ERR: print usage"; exit 1;;
-        esac
-    done
-    # users responsibility to reset OPTIND
-    OPTIND=1
-}
-
-parse_args -f xxx -c
-parse_args -f yyy
-```
-
-## Regular Expressions
-
-Bash supports regular expression matching with the binary operator `=~`.
-The match results can be accessed via the `$BASH_REMATCH` variable:
-- `${BASH_REMATCH[0]}` contains the full match
-- `${BASH_REMATCH[1]}` contains match of the first capture group
-
-```bash
-INPUT='title foo : 1234'
-REGEX='^title (.+) : ([0-9]+)$'
-if [[ $INPUT =~ $REGEX ]]; then
-    echo "${BASH_REMATCH[0]}"    # title foo : 1234
-    echo "${BASH_REMATCH[1]}"    # foo
-    echo "${BASH_REMATCH[2]}"    # 1234
-fi
-```
-> **Caution**: When specifying a `regex` in the `[[ ]]` block directly, quotes will be treated as part of the pattern.
-> `[[ $INPUT =~ "foo" ]]` will match against `"foo"` not `foo`!
-
-## Completion
-
-The `complete` builtin is used to interact with the completion system.
-```bash
-complete                    # print currently installed completion handler
-complete -F <func> <cmd>    # install <func> as completion handler for <cmd>
-complete -r <cmd>           # uninstall completion handler for <cmd>
-```
-
-Variables available in completion functions:
-```bash
-# in
-$1              # <cmd>
-$2              # current word
-$3              # privous word
-
-COMP_WORDS      # array with current command line words
-COMP_CWORD      # index into COMP_WORDS with current cursor position
-
-# out
-COMPREPLY       # array with possible completions
-```
-
-The `compgen` builtin is used to generate possible matches by comparing `word`
-against words generated by `option`.
-```bash
-compgen <option> <word>
-
-# usefule options:
-# -W <list>    specify list of possible completions
-# -d           generate list with dirs
-# -f           generate list with files
-# -u           generate list with users
-# -e           generate list with exported variables
-
-# compare "f" against words "foo" "foobar" "bar" and generate matches
-compgen -W "foo foobar bar" "f"
-
-# compare "hom" against file/dir names and generate matches
-compgen -d -f "hom"
-```
-
-### Example
-Skeleton to copy/paste for writing simple completions.
-
-Assume a program `foo` with the following interface:
-```bash
-foo -c green|red|blue -s low|high -f <file> -h
-```
-
-The completion handler could be implemented as follows:
-```bash
-function _foo() {
-    local curr=$2
-    local prev=$3
-
-    local opts="-c -s -f -h"
-    case $prev in
-        -c) COMPREPLY=( $(compgen -W "green red blue" -- $curr) );;
-        -s) COMPREPLY=( $(compgen -W "low high" -- $curr) );;
-        -f) COMPREPLY=( $(compgen -f -- $curr) );;
-        *)  COMPREPLY=( $(compgen -W "$opts" -- $curr) );;
-    esac
-}
-
-complete -F _foo foo
-```
-
-[dup2]: http://man7.org/linux/man-pages/man2/dup.2.html
-[psub]: https://tldp.org/LDP/abs/html/process-sub.html